Fish Survey At Lake Coleridge

Press, Volume CIV, Issue 30899, 4 November 1965, Page 14

Fish Survey At Lake Coleridge

The population of Lake Coleridge—both anglers and fish—will be the subject of a comprehensive survey by the Fisheries Division of the Marine Department this season.

When the high country ! lakes fishing season opens on Saturday there will be a fourman Marine Department team at Lake Coleridge to see what | happens. With the co-operation of anglers, they will begin a ! creel census which will continue throughout the season. ,; Mr M. Flain, a Marine De- ■ partment scientific officer, i said yesterday that . Coleridge was the biggest fish- . ing lake close to Christchurch . and it had a reputation for i not producing enough fish for its size. ri To find out just how many r fish are being caught, the in- > vestigating team will try to I see every fish taken by the j hundreds of anglers expected , to visit the lake at opening j week-end—the big social ! event of the fishing season. They will ask the fishermen -! how long they have fished, the methods used, how many s caught, how many kept, and I how many thrown back bei cause of poor size or condi- > tion. They will sex the fish. II measure them, weigh them. ■ I and record whether they are ■. brown trout, rainbow trout or Iquinnat salmon. Scale samples ■ [ will be collected to determine j 11 tile age of each fish, and the ; gut contents will be examined I (after weighing the fish) to II learn something about feedi j ing habits. Lone Worker 1 1 When the opening week-end I flurry of fishing has died ‘ | down the department will reI duce its staff at the lake to lone census-taker, Mr J. Wing, I who will stay there for the |; rest of the season recording I catches and information. | Mr Plain's research on Lake Coleridge will continue for at ! least two years. He wants to I know if the lake is producing j enough fish for its size, and if not. why not. He is already visiting the I

lake three days' a week to take samples of the plankton on which juvenile fish feed He also hopes to be able to map the feed areas of the : lake and discover whether there is enough food. Mr Flain has even made two dives in the lake with self - contained underwater breathing apparatus, and he plans more. He also wanLs to map the profile of the lake bottom. “By report, the lake is up to 600 ft deep,” he said yesterday. “but my preliminary work with a sounding line shows that it is more than 800 ft deep off Scamander Bay in the centre of the main lake." Movements Of Fish He plans to use an echo sounder, not only to plumb the depths of the lake, but also to detect fish. The type of echo-sounder he hopes to use can trace individual fish. In this way he will be able to tell where the fish go by day and night, and also thenseasonal movements and behaviour patterns. Mr Flain said there was some indication that the salmon schooled at times, and he hoped to be able to investigate that. If it were true, it would mean that when the salmon were schooling, anglers trying to catch them would often be easting in places where there was no hope of a strike. Physico-chemical information is to be collected, too, to discover whether there are any mineral deficiencies in the water that could be corrected by additions. "We want to get an idea of the angling pressure on the lake,” said Mr Flain, “and get some indication of what can be done to improve the fishing. The results will be made known to acclimatisation societies in the form of a